Constantly paying for other people's mistakes

So I ordered some DVD's from Ascent this morning and expected them to turn up tomorrow. To my surprise, they turned up only a couple of hours later! Excellent I thought! What wonderful service I thought. Then upon opening the box, I find that I have recieved some DVD's, only they're not the ones that I ordered. They not only have a slower write speed, but there's also less of them (100 as opposed to 110).
At this point I'm thinking "ARSE". So I write an e-mail telling them of their mistake.
20min later I recieve a reply, sorry for the inconvenience, we'll send you a Return Authorisation shortly, would you like a refund or the products you actually ordered?
Hmm, let me see, no I've changed my mind I don't need them anymore. Grr. Of course I still want what I ordered.
Only thing is, now I have to send the ones they sent me, back. Do you think they'll be footing the bill for this? Of course not. So now I have to pay the postage to send this box back to them while I STILL wait to recieve the products I ACTUALLY ordered.
OK so they gave me a standard reply with a weak apology, geez, nice.
Personally I don't think that's on, not when it's their mistake, not mine.

Some days it just pays to prepare yourself for dissapointment. If you're expecting it and it never comes, well hey, you're better off than you were.